Method of heat-sealing superimposed layers of sheet material

ABSTRACT

A stack of superimposed sheet material is advanced continuously in a predetermined path, and successive lengths of thread are advanced to it and pressed against one major side of the advancing stack for movement therewith. Spaced end portions of each length of thread are pushed through the stack so as to project in part from the opposite major side of the same and these parts are then deflected into engagement with this opposite major side and heat-sealed thereto, all during continuous advancement of the stack.

United States Patent n91 Bottcher METHOD OF HEAT-SEALING SLPERIMPOSEDLAYERS OF SHEET MATERIAL [75] Inventor: Winfried Bottcher, Leipzig.

Germany [73] Assignee: Veb Polygraph Leipzig Kombinat FuwePolygraphische Maschinen und Ausruestungen, Liepzig. German 3' Filed:Oct. 17. 1973 Appl, No: 407,070

Related US. Application Data {63] Continuation-impart of Ser. No.l64.307. July 20.

i97l. abandoned.

[52] US. Cl. 156/91; ill/21; 156/229 [5 l] Int. Cl. B32B 7/08 [58] Fieldof Search 156/91. 92. 93. M8. E79.

156/229.52l.5l3.475;227/71.8l; llZ/Zl. 79 R; 270/37. 53

[56] References Cited UNITED STATES PATENTS 154L367 Z/IJSI Kitcat I12/7) R [451 Nov. 11, 1975 3.319.863 5/[967 Dritz Z27/7l 3.514.0275/l97t) 227M! 3.6|U.U87 lU/l97l 227/7l X 3.653.570 4/1972 237/813.654.004 4/[972 Piesche I56/9l Primary E.\'umi'nerCharles E. Van HornAssistun! E\'am[nerMichael Ball Attorney. Age/u, or Finn-Michael S.Striker [57] ABSTRACT A stack of superimposed sheet material is advancedcontinuously in a predetermined path. and successive lengths of threadare advanced to it and pressed against one major side of the advancingstack for movement therewith. Spaced end portions of each length ofthread are pushed through the stack so as to project in part from theopposite major side of the same and these parts are then deflected intoengagement with this opposite major side and heat-sealed thereto. allduring continuous advancement of the stack.

4 Claims. 8 Drawing Figures U.S. Patent Nov. 11, 1975 Sheet 1 0153,919,019

INY/ENTOR. w/Nm/L'D BUTTCHE R US. Patent Nov. 11, 1975 Sheet 2 of53,919,019

FIG. 2

INV NTOR. l wm/m/eb B TTCHER .dfudhd ATTORNEY US. Patent Nov. 11, 1975Sheet 3 of5 3,919,019

FIG. 3

INVENTOR.

WWW/ED B07704 FR BY US. Patent Nov. 11, 1975 Sheet 4 of5 3,919,019

INVENTOR. Wm FRIEJ) BTTCk/[R TT T l Tl .N trukc o hp 411M.

US. Patent Nov. 11, 1975 Sheet50f5 3,919,019

FIG. 7

FIG. 8

INY/ENTOR. W/NFR/ED BOTTCHER //i'u J $44 A METHOD OF HEAT-SEALINGSUPERIMPOSED LAYERS F SHEET MATERIAL The present application is acontinuation-in-part of my earlier application Ser. No. 164,307, filedJuly 20, 1971 and now abandoned.

CROSS-REFERENCE TO RELATED APPLICATIONS Related applications Ser. Nos.213,255 (now US. Pat. No. 3,763,798) and 214,232 (now US. Pat. No.3,763,799), have been filed in my name on Dec. 29, 1971, and Dec. 30,1971, respectively, under the titles "Apparatus for Stitching SheetMaterials, and "Method for Connecting Superimposed Layers of SheetMaterial and Apparatus for Carrying out the Method."

BACKGROUND OF THE INVENTION The present invention relates generally tothe connecting of superimposed layers of sheet material to one another,and particularly to a method for effecting such a connection and to anapparatus for carrying out the method.

The invention is concerned with "binding" of books, brochures, pamphletsand the like, with the word "binding" here being used in its broadestsense to imply only the connection of superimposed sheet material layersto one another, a process which may or may not be followed (for instanceif a book is involved) by providing a separate cover, a spine or thelike.

In this broad binding" or connecting of superimposed sheet materiallayers, such as sheets of paper which may be printed or not, with oneanother it is known to either staple the layers or to stitch them withthread. The stitching with thread can be carried out in different ways,which may basically be subdivided into continuous stitching, that is insewing as with a sewing machine, or in the formation of individualstitches each of which is composed of a single length of thread spacedend portions of which are pushed through the stack of superimposed sheetmaterials so that the stitch somewhat resembles a conventional stable,with the free parts which the pushed through being sealed to theopposite side of the stack as disclosed in the present invention isconcerned in particular with this latter type of stitching. In the knownapproach to this type of stitching or thread-sealing it is known toeffect such stitching of superimposed sheet materials and subsequentlyto fold the stack along the stitching line. The prior art as disclosedGDR Pat. No. 10,106, teaches that the stack is to be advanced in adirection at right angles to the line which is to be formed by stitchingon the stack when the latter reaches a working station, and at theworking station there is located a plurality of stitching arrangementscorresponding in number to the number of stitches to be provided in thestack. When the stack is located beneath these stitching arrangements,which are located in a line coincident with the line of stitches to beformed in the stack, the latter is briefly arrested in its movement andthe stitches are provided in it while it is stationary. Thereupon thenow stitched stack is again advanced and usually moved to a foldingstation where it is folded along the line of stitches which have justbeen provided.

The self-evident disadvantage of this prior-art teaching is that theoperation must be discontinuous because each stack of sheet materialsmust be arrested while the line of stitches is formed in it. Because ofthis the throughput capacity of an apparatus utilizing this priorartteaching is considerably limited with the result that it cannot be usedeither with high-speed supplying apparatus (such as rotary printingpresses) or with highspeed user apparatuses. On the one hand the supplyof stacks of material would arrive too fast to be handled, and on theother hand the supply of stitched stacks to a high-speed user apparatuswould be too slow. Moreover, the technical requirements which must befulfilled in this type of apparatus are out of all proportion to theeconomy of operation which can be achieved with it, especially becausesuch apparatus requires as many stitching devices as stitches must beformed in each and every stack of sheet materials.

A further disadvantage is the fact that the technical complexity as wellas the physical dimensions of these stitching devices make it impossibleto locate them so closely together in a row that the stitches can be provided immediately consecutively, as is often desired.

According to a further prior-proposal made in US. Pat. No. 3,654,004, arotary stitching device is provided which forms a row of stitches in thestack of sheet materials which is advanced in the direction in which therow is to be formed. In this prior-art device the sheet material orsheet materials move between a pair of rollers over one of which thethread required for forming the stitches is placed, which thread is tobe cut into pieces of requisite length also called thread changes whoseopposite ends are then pushed through the stack, to be secured theretoin known manner.

With the type of stitching here under discussion, it is a basicrequirement that a length of thread of requisite elongation be cut off,engaged and maintained taut on a major surface of the sheet material orstack of sheet materials, until it is pushed by the needles of thestitching device through the sheet material. The needles are providedwith substantially wedge-shaped recesses in their leading ends which areplaced over the end portions of the thread and then push the endportions through the stack of sheet materials. Because of the necessityto hold each thread piece taut on a surface of the stack until its endportions are pushed through the latter, it is necessary that the threadsupply arrangement and the needles, if both are to be utilized forforming stitches in continuously advancing stacks of sheet materials sothat both devices must be mounted for rotation, be capable of rotatingabout the same axis. The thread supply device must withdraw the threadfrom a supply, such as a bobbin and must sever it into pieces ofrequisite lengths. This, of course, requires that a cutting device mustbe provided in addition. The thread supply device must be constructed asa hollow drum which on its outer periphery is provided with clampingdevices and cutting devices for the thread, and inwardly must havejournals for the needles which must always be moved radially withreference to a counter cylinder or roller, whereas in the interior ofthe hollow drum there must be provided control devices which effect themovement of the cutting device and the needles in a sense causing thelatter to push the end portions of the thread increments through thestack. On the other hand it is necessary that the diameter of the hollowdrum or roller be as small as possible be cause the number of threadholders and needles increases as the diameter of the drum increases, butthis in turn is a requirement which contradicts with the necessity forhaving adequate space in the interior of the drum for the necessarycontrol devices. The result in the prior art is a compromise accordingto which the thread supply device as well as the control devices aremade as small as possible, but on the other hand are given a reasonablelife expectancy and reliability consistent with the requirement thatthey be as small as possible.

Once the end portions of a respective thread piece have been pushedthrough the stack they will project in part beyond the opposite majorsurface thereof. These parts must then be deflected into engagement withthis opposite major surface and must be sealed thereto, and usually thescaling is effected as heat sealing with the thread being aheat-bendable thread of known type, e.g. polyesters, cellulosetriacetate, polyethylene, polyproprylene, polymiychloride and mixedpolyesters. Such materials are, for example, disclosed in British Pat.No. 1,048,847 to which reference may be had for further details. Themeans for effecting the deflection and the bonding utilizes stationaryinstrumentalities over which the stack is moved.

The second-mentioned prior-art approach, utilizing a rotating threadsupply arrangement and needles which are guided and controlled in it,permits a substantial increase in throughput over the first-mentionedarrangement. However the construction is complicated as pointed outabove, and all components are located within a very small space, whichfacts not only facilitate breakdowns but make it exceedingly difficultto effect repairs when breakdowns do occur. All in all, the priorartdevice of the second type therefore does not meet the requirements madeas to speed and reliability especially in continuously operatingmachines. In order to avoid a complete shut-down of such a machine itwould be necessary to have at least two of the secondmentioned stitchingdevices which can operate in parallelism and of which one can take overwhile the other is being repaired. In addition it would be necessary toprovide means for switching over the flow of sheet material stacks fromone to the other of the stitching devices, depending upon which of themis operative at any given time. All of this of course is expensive andthe loss of reliability is disadvantageous. [t is also found that thedisadvantages mentioned above occur at the output side of printingmachines utilizing such stitching arrangements, and it is furtherpointed out that the control devices for the thread severing device andfor the needles are subject to rapid and considerable wear because ofthe movements involved, so that the advantage of being able to threadstitch a stack of sheet materials during continuous movement inaccordance with the second-mentioned prior-art approach is almost orcompletely counteracted by these disadvantages.

SUMMARY OF THE INVENTION It is thus a general object of the presentinvention to overcome the disadvantages of the prior art.

More particularly it is an object of the present invention to provide animproved method of connecting su perimposed layers of sheet materialwhich advance continuously in a predetermined path, which method is notpossessed of these disadvantages.

in pursuance of the above objects, and of others which will becomeapparent hereafter, one feature of the invention resides in a method ofsealing superimposed layers of sheet material which advance continuouslyin a predetermined path. This method comprises the steps of continuouslyadvancing a stack of superimposed sheet materials in a predeterminedpath, and pressing a cut length of thread which forms a stretched threadclamp against one major side of the advancing stack for movement withthe same. While the length of thread is held in place on the advancingstack, spaced end portions of the length of thread are pushed throughthe stack so as to project in part from the opposite major side thereof.The projecting parts are deflected into engagement with this oppositemajor side and sealed thereto during the continuous advancement of thestack in the path.

The deflecting and sealing effected by stationary instrumentalities or asingle instrumentality, and it is advantageous according to a furtherconcept of the invention that the stack is provided with openings duringthis advancement but before the end portions of the pieces of thread arepushed through the stack, so that subsequently these end portions can bepushed through the thus-provided openings. This is not, however, aprerequisite of the present invention and constitutes merely oneadvantageous aspect.

It will be appreciated that the present invention essentially differsfrom the aforedescribed prior art by pressing thread pieces of requisitelength against a surface ofthe advancing sheet material stack, andmoving these thread pieces with the advancing stack until they reach adevice which pushes their spaced opposite end portions through thestack. Because of this, a physical and local separation of the threadsupply and cutting device and of the device which actually effectsstitching of the thread piece ends through the stack, can be readilyobtained; this makes it possible to construct the various devices insuch a manner that they will have optimum dimensions without influencingone another of interfering with one another. This avoids the necessityfor excessive miniaturization and the concomitant disadvantage of readysusceptibility to breakdowns. More over, in an apparatus for carryingout the present method the various constituent components and devicescan all be so mounted because of the space availability that any onedevice or component can be readily removed and replaced withoutinterfering with or being interfered by other devices or components, andof course also being readily accessible.

As mentioned earlier, materials suitable for the thread lengths whichare used as thread staples, are known from British Pat. No. l,048,857.They include polyesters and, cellulose triacetate as materials having ahigh melting point, and polyethylene, polypropylene, polymiylcloride andmixed polymers as materials having a low melting point.

It is important that the thread lengths be both relatively thin andflexible. because otherwise the back of a stack of sheets connected withthe thread staples constituted by these thread lengths (e.g. the back ofa book) will become excessively thick. To meet these requirements, thethread lengths are cut from a thread which is composed of a plurality oftheir filaments which may all be of one of the aforementionedheatsealable materials, or different filaments may be of different onesof these materials. However, only one or some of the filaments may be ofsuch materials, and the remaining filaments of the thread may benon-scalable material, for instance cotton. The filaments may be spuntogether, twisted together or braided together. Thus. non-scalablefilaments may surround a core of one or more heat-scalable filaments.

According to the present invention it is advantageous that an endlesstransporting device be provided which extends in parallelism at least ina portion of its path with a transporting device for the stack ofsuperimposed sheet materials, with sections of the endless transportingdevice entering into recesses provided in the periphery ofa continuouslyrotating thread supply device whose periphery contacts and rolls on onemajor surface of the stack of sheet material. The sections thus enterinto such recesses where they contact a thread piece of requisite lengthwhich spans the respective recess, pressing this thread piece againstthe one major surface of the stack and pulling it loose from engagementwith the thread supply device during continued advancement of theendless transport device together with the stack. The transportingdevice is advantageously configurated as an endless chain which ismounted for movement in parallelism with the direction of advancement ofthe stack of sheet materials at a speed corresponding to the speed ofadvancement of the stack. The chain will have sections carrying pressureelements which contact the respective thread pieces pressing themagainst the one major surface of the stack and having a width or lengthin the longitudinal direction of the thread piece which is smaller thanthe distance between two cooperating needles of the subsequentlyarranged stitching device, which needles engage the opposite endportions of the thread piece and push it through the stack forming athread clamp. The movement of the needles is so synchronized with themovement of the endless chain that the two needles will always pushthrough the sheet material at the opposite ends of the respectivepressing element, thereby contacting and pushing through the stack thespaced end portions of the thread piece which is located beneath andbeing held in place by the pressing element. The center portion of theclamp to be formed continues to be held during this process by thepressing element.

It is usual procedure that the stack of sheet material layers ispositioned on a conveyor belt or the like by which it is advanced in itspredetermined path. According to the present invention such a conveyorbelt may utilize an upper and a lower conveyor which engage the stackbetween them in order to transport the stack without slippage. However,in place of the belts it is of course possible to use endless chains,just as only a lower belt may be provided for support of the stackwhereas the function of the upper belt may be taken over by the endlesschain whose pressing elements engage and hold the respective threadpieces. This is all the more readily possible because the endless chainis advanced at the same speed and in the same direction as the lowerconveyor belt supporting the stack. Such use can be further facilitatedby providing on the contact or pressing elements friction-promotingsurfaces which should remain clean at all times and which contact thestack.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a somewhat diagrammatic sideview of an apparatus according to the present invention as seen fromline I-I of FIG. 2;

FIG. 2 is a top-plan view of FIG. 1;

FIG. 3 is a fragmentary end view, on an enlarged scale, of FIG. 1 asseen in the direction of the arrow A in FIG. 1;

FIG. 4 is a fragmentary enlarged detail view of the detail shown in thecircle IV of FIG. I;

FIG. 5 is a fragmentary enlarged view of the detail shown in the circleV of FIG. 1;

FIG. 6 is a fragmentary enlarged view of the detail shown in the circleVI of FIG. 1;

FIG. 7 is a fragmentary plan view of an apparatus according to a furtherembodiment of the invention; and

FIG. 8 is a side view of the apparatus shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing firstly theembodiment illustrated in FIGS. 1-6 it will be seen that the inventionis described by way of example on hand of an arrangement or apparatusfor stitching stacks of superimposed sheet materials which (irrespectiveof the previous treatment which they have received) are subsequentlyintended to be folded once more along the line of stitches which isformed on them. Thus, the output for instance of printing machines canbe directly supplied to the novel apparatus, or it can undergopreliminary folding except for the final holding before it reaches thenovel apparatus. It is emphasized. however, that the novel apparatus andmethod can also be utilized for stitching stacks of sheet materialswhich have already received the final fold but which must then, ofcourse, be unfolded again and advanced on a proper support to theapparatus for stitching purposes.

Keeping this in mind, and now referring to FIG. 1, it will be seen thatreference numeral 1 identifies two stacks of superimposed sheetmaterials which are to be continuously advanced in the direction of thearrow A, that is from the left towards the right in FIG. I. These stacksmove between a lower conveyor belt 2 and a cooperating upper conveyorbelt 5 between the juxtaposed runs of which the stacks 1 are engaged andadvanced. The lower conveyor belt is composed of belt portions 20, 2b,2c and 2d as shown in FIG. 3, which pass around axially parallel spacedrollers 3 and 4. The upper belt 5 is similarly constituted by beltsections 50, 5c and 5d which are trained about upper rollers 6 and 7 andwhich are respectively in contact with the corresponding belt sections2a, 2c and 2d of the lower belt 2. Suitable drive means (not illustratedbecause conventional) are provided which drive the rollers 4 and 7 atidentical circumferential speed but in mutually opposite direction(compare the arrows in FIG. I) so that the abutting runs of the belts 2and 5 move in one and the same direction, namely towards the right inFIG. 1. Thus, the stacks l are transported between the belts 2 and 5without slippage.

Upwardly of the belt section 2b an endless chain 8 is provided which istrained about sprocket wheels 9, 10 and II and rotates in the samedirection and at the same speed as the adjacent belt sections a and 5c.The chain 8 is provided at identical distances with pressure springs I2of springy sheet metal or other sheet material. which are so mountedthat they will press above the belt sections 2b and 2c at the middle andalong the so-called sealing line 5-5 (see FIGS. 2 and 3] lightly againstthe upper surface of the stack 1. The springs 12 which contact thestacks 1 thus move with the latter without performing any relativemovement with respect to the stacks l. A pressure rail or member 13exerts a uniform pressure upon the support rollers of the chain 8 sothat the latter cannot be deflected upwardly by the pressure of thestacks 1 against the springs 12. If desired, corresponding rails ormembers can also be provided along or laterally adjacent to the sealingline 8-5 beneath the stacks I, that is beneath the run of the conveyor 2which supports the stacks I, in order to prevent the stacks 1 from beingdownwardly deflected at least at or in the region of the sealing lineSS.

Midway intermediate the ends of the roller 6 there is mounted in thisembodiment a punching disc 14, and beneath it, also midway of theopposite ends of the roller 3 which is located below the roller 6, acooperating counter disc 15, both being shown more clearly in FIG. 3.The disc 14 is provided on its periphery with a plurality ofequiangularly distributed needles 140 which each enter into acorresponding small recess. aperture or groove 150 provided in theperiphery of the cooperating disc 15. Thus, a stack 1 passing betweenthe discs I4 and into the space between the belts 2 and 5, is providedwith apertures or perforations la (see FIG. 4) along the line S--S ofFIG. 2, and these perforations Ia are so spaced from one another in thedirection of elon gation of the line SS that any two consecutive perforations la have from one another a distance which corresponds to thelength of the center portion ofa clamp 25 (see FIGS. 5 and 6). Any twoconsecutive perforations la are also spaced from one another in thedirec tion of the line 8-5 by a distance which is somewhat greater thanthe elongation of the springs 12 in the same direction, it beingunderstood that these springs 12 will subsequently engage the stack 1intermediate the consective ones of the perforations la. Thisprepunching or perforating of the stack 1 is intended to facilitate thesubsequent passage of two pushing members or needles 23 (see FIG. 5) ofa stitching device 22 through the stack 1, which needles push the spacedopposite end portions of a thread piece through these apertures orperforations Ia. However, it is emphasized that such prepunching andproviding of the apertures Ia can be omitted without in any wayinfluencing the validity of the basic inventive concept.

Reference numeral 16 in FIG. I identifies a bobbin or similar supply ofa thread I7 which in the illustrated embodiment is assumed to be ofheat-sealable type, for instance a filament or a rnulti-filament of athermoplastic material. A thread supply disc 18 withdraws the thread 17from the bobbin I6 and a thread cutting device l9 cuts it intosuccessive pieces 20 the length of which corresponds to the lengthrequired for forming a single clamp as shown in FIGS. 5 and 6. Thesevered thread pieces 20 are maintained in taut condition (see FIG. 4)on the periphery of the thread supply disc I8 by engagement withclamping springs 21, being so located that each thread piece 20 spans arecess 27 provided in the periphery of the disc I8. The arrangement ofthe recesses 27 corresponds with the arrangement of the spring membersI2 on the chain 8 in such a manner that, when the chain 8 and the discmember 18 are synchronously driven, there will always be one springmember 12 entering into a recess 27 of the member 18 5 before the thread17 is tautened across the associated recess 27 and held in tautcondition by the clamping springs 21 upon cutting from the remainder ofthe thread 17.

The periphery of the disc member 18 rolls on the upper surface of thestack l, and this results in the position IV shown in FIG. I, which isillustrated in more detail in FIG. 4. It will be seen that when themember 18 turns. the pressure spring 12 which is located in therespective recess 27 and presses the thread piece 20 associatedtherewith against the surface of the stack 1, will move along with thestack I in a straight line whereby the opposite end portions of thethread piece 20 are pulled loose from the clamping springs 21. Becausethe spring 12 is located precisely over the middle portion of the threadpiece 20, i.e.. over that portion which will become the back of thefinished thread clamp 25, mid way between two apertures la in the stack1 (if such apertures are previously provided, which is not necessary asalready pointed out) continuous advancement of the stack with the threadpiece 20 held thereon by the associated spring member 12 causes thethread piece 20 to reach a thread stitching device 22 of any desiredconstruction. This is shown in FIG. 5 and it will be seen that here thetwo associated needles 23 push the end portions of the thread piece 20which project in opposite directions beyond the associated spring member12, through the aperture la (or form such apertures and push the endportions through them if apertures have not been previously prepunched).Moreover, the needles 23 do not perform any relative movement withrespect to the continuously advancing stack 1, but instead advance alongwith the stack 1. This means that at the position V of FIG. 1 it ispossible to use continuously rotating needle carrying discs driveutilizing pairs of needles such as disclosed in one of theaforementioned copending related applications. The drawing clearly showsthe somewhat wedgeshaped recesses in the free needle ends, whichstraddle the thread movement end portions.

In FIG. 5, in which a device such as the one just men tioned above withrespect to the copending application is utilized, the deepestpenetration of the needles 23, immediately before their upward movementfor retracting purposes is illustrated. By contrast. FIG. I shows thebeginning of their movement into and through the stack 1. It will beseen in FIG. 5 that when the needles 23 have reached the illustratedposition, the end portions of the thread pieces 20 have been pushedthrough the perforations Ia by the needles 23 of the device 22, wherebythe thread increment 20 has been transformed into a stitch 25 whoseconfiguration essentially resembles that of a conventional metal staple(clamp). The end portions 26 of the stitch 25 pass vertically throughthe stack 1. On continued movement of the stack 1 the needles 23 movealong with the same and are simultaneously withdrawn in verticaldirection upwardly through and out of the stack 1, with the form andposition of the stitch 25 being maintained unchanged because the springl2 continues to press the center portion of the thread piece 20 againstthe upper surface of the stack 1.

with controlled needles, or a parallel flange needle In FIG. 6, whichillustrates the encircled portion VI of FIG. I, l have illustrated thebeginning of the operating step at which the parts of the end portions26 which project beyond the lower side of the stack 1, are deflectedinto engagement with this lower side and sealed thereto. For thispurpose there is provided beneath the stack 1 coincident with thesealing line 8-5 a heated sealing or bonding element 24 which is springmounted or mounted for floating movement with very little spacing fromthe underside of the stack 1. The edge portion 24a of the member 24which forms oppositely the direction of advancement of the stack 1 isslightly inclined as illustrated, and as the projecting parts of the endportions 26 move against it, they are deflected in upward direction, andby contact with the heated material of the member 24 they are sealedagainst the underside of the stack 1. Such sealing by heat is of coursealready well known and it is emphasized that sealing could also beeffected in other manner, for instance by separately applying anadhesive. Once any one stitch moves in downstream direction beyond themember 24, the material of the stitch can cool and finally theassociated spring member 12 is lifted off the stitch due to the changein the direction of movement of the chain 8 as the latter passes aroundthe sprocket I0. Ultimately, the now stitched stack 1 is released by thebelts 2 and 5 and can be received in a receptacle or can be passed on toother processing stations of user stations.

In FIGS. 7 and 8 I have illustrated one additional embodiment among themany which can be realized without departing from the scope and conceptof the present invention. Here there are provided at opposite sides ofthe sealing line 8-8, extending in parallelism with the same, two wallsor plates 28 and 29. Located intermediate these are the non-illustratedthread supply arrangements, thread stitching arrangements and threadsealing arrangements which may operate in the same manner as previouslydescribed.

A toothed belt 30 which is endless is trained about two wheels 31 and 32of which the latter is driven and journalled on the plate 28. An equallylong endless toothed belt 33 is trained about the wheels 34 and 35 ofwhich the latter is driven and both of which are journailed in the plate29. The belts 30 and 33 are located at opposite sides of the sealingline 8-8 and in accordance with the present invention the journal boresfor the wheels 31 and 32 on the one hand, and the wheels 34 and 35 onthe other hand, are each spaced from one another by identical distancesand located at the same level, but are offset longitudinally by adistance D (see FIG. 7) which corresponds to the length of the desiredthread pieces and therefore also to the spacing of the successivepressure-exerting elements which engage consecutive ones of the threadpieces.

A plurality of carrier bolts 37 extend through the gap defined betweenthe upper and lower runs of the belt 30, being spaced from one anotherat the aforementioned distance D, and similar bolts 38 extend throughthe gap defined between the upper end lower run of the belt 33. Springcarriers 36 are pivotally mounted on the bolts 37 and 38 and to thesecarriers 36 there is mounted by means of two rivets 39 a spring plate 40which, as shown in FIG. 8, presses each thread piece against therespective stack 1.

In FIG. 8, which is a side-elevational view of FIG. 7, the plate 29 hasbeen omitted for the sake of clarity. It will be appreciated that due tothe coupling of the belts 30 and 33 via evenly distributed pivotablespring carries 36 a drive of the belt 30 by means of the wheel 32 issufficient to take along the belt 33. During such movement the carrier36 will always maintain (due to 5 their pivotal mounting) the identicalrelative position in space. In FIG. 8 it is shown that each spring plate40 will move vertically onto a thread piece which is held spanning arecess 27 of a disc member 18 (as described with respect to FIG. 4) andwill press the thread piece against the upper surface of the stack 1which in turn is advanced in the manner already described, for instanceby means of the belt 33 shown in FIG. 8.

It will be understood that each of the elements de scribed above, or twoor more together, may also find a useful application in other types ofconstruction differing from the types described above.

While the invention has been illustrated and described as embodied in anapparatus of the type discussed, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis the foregoing will so fully reveal the spiritof the present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

I. A method of thread-sealing superimposed layers of sheet materialwhich advance continuously in a path. comprising the steps ofcontinuously advancing a stack of superimposed sheet material in astraight-line path; withdrawing a heat-sealable thread from a supply;severing a length of thread from said heat-scalable thread at a locationspaced from said path; moving the severed length of thread in stretchedcondition to and in direction lengthwise of said path and of thedirection of advancement of said stack; placing the stretched length ofthread onto and pressing it against one major side of the advancingstack so that it moves with the same; pushing spaced end portions ofsaid length of thread through said stack so as to project in part fromthe opposite major side thereof; deflecting the projecting parts intoengagement with said opposite major side; and heat-sealing each of saidprojecting parts directly to said opposite major side of said stackduring the continuous advancement of said stack in said path.

2. A method as defined in claim I, wherein the steps of deflecting andsealing comprise moving said projecting parts past and effecting theircontact with a stationary abutment located adjacent said path proximalto said opposite major side.

3. A method as defined in claim 1, wherein the step of heat-sealing saidprojecting parts to said opposite major side comprises heat-softeningsaid parts and urging them against said opposite major side.

4. A method as defined in claim 1, and further comprising thepreliminary step of forming openings in said stack during saidadvancement thereof and at locations of said stack where said endportions are to be pushed therethrough.

1. A METHOD OF THREAD-SEALING SUPPERIMPOSED LAYERS OF SHEET MATERIALWHICH ADVANCE CONTINUOUSLY IN A PATH, COMPRISING THE STEPS OFCONTINUOUSLY ADVANCING A STACK OF SUPERIMPOSED SHEET MATERIAL IN ASTRAIGHT LINE PATH, WITHDRAWING A HEAT-SEALABLE THREAD FROM A SUPPLY,SEVERING A LENGTH OF THREAD FROM SAID HEAT-SEALABLE THREAD AT A LOCATIONSPACED FROM SAID PATH, MOVING THE SEVERED LENGTH OF THREAD IN STRETCHCONDITION TO AND IN DIRECTION LENGTHWISE OF SAID PATH AND OF THEDIRECTION OF ADVANCEMENT OF SAID STACK, PLACING THE STRETCHED LENGTH OFTHREAD ONTO AND PRESSING IT AGAINST ONE MAJOR SIDE OF THE ADVANCINGSTACK SO THAT IT MOVES WITH THE SAME, PUSHING SPACED END PORTIONS OFSAID LENGTH OF THREAD THROUGH SAID STACK SO AS TO PROJECT IN PART FROMTHE OPPOSITE MAJOR SIDE THEREOF, DEFLECTING THE PROJECTING PARTS INTOENGAGEMENT WITH SAI OPPOSITE MAJOR SIDE, AND HEAT-SEALING EACH OF SAIDPROJECTING PARTS DIRECTLY TO SAID OPPOSITE MAJOR SIDE OF SAID STACKDURING THE CONTINUOUS ADVANCEMNT OF SAID STACK IN SAID PATH.
 2. A methodas defined in claim 1, wherein the steps of deflecting and sealingcomprise moving said projecting parts past and effecting their contactwith a stationary abutment located adjacent said path proximal to saidopposite major side.
 3. A method as defined in claim 1, wherein the stepof heat-sealing said projecting parts to said opposite major sidecomprises heat-softening said parts and urging them against saidoppOsite major side.
 4. A method as defined in claim 1, and furthercomprising the preliminary step of forming openings in said stack duringsaid advancement thereof and at locations of said stack where said endportions are to be pushed therethrough.